As he desperately tries to squash a popular rebellion, Libyan ruler Moammar Gaddafi is banking on the loyalty of a close circle of relatives and security officials whose personal fates depend on his survival, according to U.S. officials and analysts.

Among them are four of his sons and two longtime spy chiefs accused of directing a series of assassination and terrorist plots during Gaddafi's four decades in power. While numerous Libyan diplomats and government officials have defected or abandoned Gaddafi in recent days, analysts said it is unlikely that his inner core will follow suit.

"The people who are in the bunker with him, they have pretty good reasons for sticking by Gaddafi," said John Hamilton, a Libya expert with Cross Border International, a British publishing and consulting firm that specializes in North Africa. "It's a bit late for the sons to revolt against their father . . . There's really nowhere for the others to turn, either."

For years, the Gaddafi children have jockeyed for influence in hopes of replacing their father, a competition that Gaddafi has encouraged by refusing to anoint a successor and purging the government of potential rivals. But the Gaddafi sons appear to have put aside their jealousies in an attempt to save their father - as well as themselves, analysts said.

The second eldest, Saif al-Islam, has appeared on television twice to exhort Libyans to rally to Gaddafi's defense. Saadi, a former professional soccer player, has overseen countermeasures against protesters in eastern Libya.

Gaddafi's most influential allies may be two aging deputies well known to U.S. officials: Abdullah al-Senussi, the former chief of military intelligence, and Foreign Minister Musa Kusa, formerly Libya's top external spy.

Senussi, who is also a brother-in-law to Gaddafi, was convicted in absentia in France for masterminding the 1989 bombing of a French passenger airplane in which 170 people died. Although his current job has not been spelled out publicly by the Libyan government, analysts said he operates in effect as a chief of staff to Gaddafi on security matters. Human rights groups have accused him of orchestrating Libya's repression of political dissidents.

Herman J. Cohen, a former U.S. diplomat who met with Senussi several times as a private businessman in the late 1990s and early 2000s, said the security chief was "the most paranoid" member of Gaddafi's inner circle when it came to dealing with Washington but eventually warmed to the idea.

"He was clearly very influential on all subjects," Cohen said.

In 2003, Senussi and Kusa were both accused of attempting to carry out an order from Gaddafi to assassinate Saudi Arabia's Crown Prince Abdullah, now the king. The plot was disrupted when two Libyans involved in the case gave separate confessions to Saudi and U.S. officials. The findings set back, but did not thwart, Libya's long-standing efforts to repair relations with Washington.

Kusa, who holds a master's degree from Michigan State University, was instrumental in negotiating the restoration of diplomatic ties with the United States in exchange for Libya's agreement to give up its nuclear weapons program. He was named foreign minister in 2009 but "still appears to hold sway on certain intelligence and security officials," according to a cable written that year by the U.S. Embassy in Tripoli.